Dehghani et al. Marine Biodiversity Records (2016) 9:44 DOI 10.1186/s41200-016-0039-0

MARINE RECORD Open Access Otolith dimensions (length, width), otolith weight and fish length of Sardinella sindensis (Day, 1878), as index for environmental studies, , Mohsen Dehghani1,3*, Ehsan Kamrani1, Ali Salarpouri2 and Sana Sharifian1,3

Abstract Background: Sardines are the most important commercial fishes for Iran. However, information about biology and ecology of sind sardine in Persian Gulf and Sea is scarce. Methods: In this study, relationship between fish length and otolith length, -width and -weight of Sardinella sindensis from Bandar Lengeh and , Persian Gulf were analyzed. In total, 128 and 120 fishes collected from Commercial catches during March 2011- February 2012 in the Bandar Lengeh and Qeshm Island respectively. Results: There were no significant differences between left and right otolith (t-test, P > 0.05) or between males and females otoliths (ANCOVA, P > 0.05). For these reasons, only right otoliths were used for next analysis and data of both sexes were pooled. Relationships between fish length and otolith length, width and weight were described by linear regression models and high correlation was shown for all relationships. The highest correlation was between fish length and otolith length (Bandar Lengeh, R2 = 0.8722; Qeshm Island, R2 = 0.8661) and relationship between fish length and otolith width showed less correlation than other relationships (Bandar Lengeh, R2 = 0.7355; Qeshm Island, R2 = 0.7275). Conclusions: The result from this study shows that fish length and otolith growth have a positive relationship, so can be a useful tool to evaluate the growth of fish and fish stocks and finally fisheries management. Keywords: Fish length, Otolith, Sardinella sindensis, Persian Gulf

Background population and for fisheries management, furthermore the The inner ears of all teleost fishes contain three calcified analysis of microstructure otolith have greatly developed structures, which acts as balance and hearing organs for stock identification, feeding ecology of predators, and (Popper et al. 2005). Otoliths serve as a permanent rec- the determination of migration direction in fishes species ord of the life history of an individual fish (ICES 2004), (Campana & Thorrold, 2001; Mendoza 2006, McFarlane and they hold a wealth of information on daily age, size, et al. 2010). The application of otolith only is not re- growth and ontogeny of fishes (Gerard & Malca, 2011). stricted to ichthyology, but also extended widely for some The otoliths continue to grow throughout their life and aspects of palaeontology, stratigraphy, archaeology and do not resorb in time of stress (Yaremko, 1996; Mendoza, zoogeography (Tuset et al. 2008). The size and shape of 2006). Thus, they are one of the most reliable tools for otoliths are variable according to species and size of fish identification of growth rates, structure of age in a certain (Eroglu & Sen, 2009). The relationship between fish length and otolith dimensions, can be useful to estimate the size * Correspondence: [email protected] and age of prey collected from stomach and feeding habits 1 Department of Marine Biology, Faculty of Basic Sciences, University of of fishes (Hunt, 1992; Granadeiro & Silva, 2000; Khodadai Hormozgan, P.O.Box: 3995, , Iran 3Young Researcher and Elite Clube, Islamic Azad University, Bandar abbas & Emadi, 2004, Pombo et al. 2005, Rizkalla & Bakhoum, Branch, P.O.Bbox: 79159-1311, Bandar Abbas, Iran 2009; Javor et al. 2011). Full list of author information is available at the end of the article

© 2016 Dehghani et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Dehghani et al. Marine Biodiversity Records (2016) 9:44 Page 2 of 6

Sardines are small pelagic fishes that live in coastal wa- The aim of this study was to gain understanding of the ters of many sea and ocean. They feed on planktons and relationships between fish length and otolith dimensions are eaten by other fishes, so they are important in marine of S.sindensis, through regression analysis. food web (Emmett et al. 2005; Salarpouri et al. 2009). In addition, sardines are consumed as fresh meal for humans Methods and as commercial powder (Bennet et al. 1992; Hill et al. Fishes were selected, randomly, from commercial 2005; FAO, 2011). Many studies for sardine genus have catches using purse seine nets. A total of 120 fishes were been performed on the otolith structures, such as growth collected from coastal waters of Bandar Lengeh (26°55′ and mortality estimation, identification of fishes, deter- 27″N 54°88′14″E) and 128 fishes from Qeshm Island mine the fish stock and trace migration pathway of fish (26°41′43″N 55°37′06″E) in North of Persian Gulf (Nair, 1949; Krzeptowski, 1983; Cergole & Valentini 1994; (Iran) during March 2011 to February 2012 (Fig. 1). Butler et al. 1996; Watanabe & Nakamura, 1998; Gaughan Fishes were transported to the laboratory of Persian Gulf & Mitchell, 2000, Silva et al. 2008; Mehanna & Salem and Oman Sea Ecological Research Institute, Bandar 2011; Ward et al. 2012; Dehghani et al. 2015). According Abbas. to FAO (2011), Sardinella sindensis is the most important First, total fish length was measured to the nearest commercial fish for Iran and Pakistan. However, a few 0.1 mm, and then sex determination was done under studies have been performed on the structure of otoliths stereomicroscope. Chi-square test was performed for sex in S.sindensis from Iran. The age and growth of S.sindensis differences. Otoliths were extracted from heads of sam- was studied using annual rings of otoliths from Persian ples, cleaned and dried. Otolith weight was measured by Gulf and Oman, Iran by Dehghani et al (2015). Otoliths using digital balance to the nearest 0.0001 g. For measur- tend to grow linearly in length and width with increasing ing the otolith size, images were taken under a stereo fish size, and to grow linearly in thickness and weight with microscope linked to a video camera (Motic Image Plus increasing fish age (Donkers, 2004). For most species, 2), and otolith length and -width were measured using im- the relationship between otolith length and fish length aging software (Motic 2) to the nearest 0.01 μm. Otolith can be described by a simple linear regression (Harvey length is the distance from the midpoint of the rostrum at et al. 2000). point A through the primordium to the posterior edge at

Fig. 1 Sampling areas of Sind sardine, Sardinella sindensis, Bandar Lengeh and Qeshm Island, Persian Gulf, Iran Dehghani et al. Marine Biodiversity Records (2016) 9:44 Page 3 of 6

Fig. 2 Otolith of S. sindensis, distance between point A and B indicating otolith length and distance between point C and D indicating otolith width point B. Width is the distance perpendicular to the length sexes were pooled. Otolith length, -width and -weight passing through the primordium (Fig. 2) (Javor et al. measurements in addition fish length and weight are re- 2011). Differences between left and right otolith were corded in Table 1. tested by paired t-test and between males and females by Relationships between fish length and otolith length, using ANCOVA (Matic-Skoko et al. 2011). ANOVA was -weight and -width were described by regression model used to test for significant differences in area. Relation- and linear equation. The equation for otolith length and ships between total fish length and otolith length and fish length was (OL = 171.51 TL+ 257.63; R2 = 0.8661) -width described by linear equation as TL = a (L) b, where for Qeshm Island and (OL = 165.06 TL+ 401.64; R2 = TL is total fish length, L is otolith length or otolith width, 0.8661) for Bandar Lengeh. Regression models and linear and a, b are constant coefficients. For express relationship equations of all relationships are shown in Figs. 4, 5 and between total length fish and otolith weight was used a linear equation like above equation that described as TL = a (OW) b, where OW is otolith weight. Regression 9 Qeshm Island method was analyzed by using Excel software (version 8 male 7 2007) for determining the relationships between fish 6 female length and otolith length,-width and -weight. 5 n=128 4 3 2 Results Number of fish 1 In total, 128 fishes from Qeshm Island and 120 fishes 0 from Bandar Lengeh collected (Fig. 3). Chi-square test was performed assuming equal sex ratio and results with a degree of freedom, did not show significant differences 2 2 Bandar Lengeh between the sexes (X = 1.2, df =1, p > 0.05) and (X = 10 male female 1.125, df =1, p > 0.05) for Bandar Lengeh and Qeshm, 8 n=120 respectively. 6 Minimum-maximum and mean fish lengths for Bandar 4 Lengeh were 8.1-18.3 and 12.7 cm respectively and those 2 for Qeshm were 7.9-18.6 and 12.9 cm, respectively. All Number of fish 0 measurement of left and right otoliths were tested and no significant differences were observed between left and right otolith (t-test, P > 0.05) and between otoliths of female and males (ANCOVA, P > 0.05), therefore, only Fig. 3 Number of S.sardinella collected from Bandar Lengeh and Qeshm Island (Persian Gulf) during March 2011 to February 2012 right otolith used for next analysis and data of both the Dehghani et al. Marine Biodiversity Records (2016) 9:44 Page 4 of 6

Table 1 Maximum, minimum, mean and standard deviation (SD) of fish length and otolith length, -width and -weight of S.sindensis from Bandar Lengeh and Qeshm Island (Persian Gulf) Area Number Minimum Maximum Mean SD Bandar Lengeh Total fish length (cm) 120 7.9 18.6 13 2.7 Otolith length (μm) 118 1620.06 3389.02 2503.06 511.37 Otolith width (μm) 118 954.24 1504.88 1250.78 153.52 Otolith weight (g) 118 0.0004 0.0026 0.0013 0.00061 Qeshm Island Total fish length (cm) 128 8.1 18.3 12.9 2.7 Otolith length (μm) 124 1610.28 3556.98 2533.7 476.5 Otolith width (μm) 124 973.43 1533.05 1237.7 132.8 Otolith weight (g) 124 0.0003 0.0027 0.0014 0.00064

6. There were no significant differences in these analyses from Australia (Gaughan et al. 2008) and other fish spe- for two areas (ANOVA, P > 0.05). cies (Hunt, 1992; Megalofoou 2006; Ilkyaz et al. 2011). In current study, results of testing the difference between right and left otoliths showed no significant dif- Discussion ference, and no significant difference between males and In this study, relationship between fish length and otolith females otoliths. In addition, this test was similar for the length, -width and -weight was analyzed by linear model. two sampling regions. These results agree with results of Otolith dimensions and weight was linearly correlated to other studies (Jawad et al. 2011), but differ from studies total fish length. Relationships between fish length and done on Sardina Pilchardus from Adriatic Sea, Crotia otolith length for each area showed highest positive cor- (Zorica et al. 2010), Sardinops sagax from west coast of relation, that is similar to results of Sardina Pilchardus North America (Javor et al. 2011) and were different from Adriatic Sea, Crotia (Zorica et al. 2010), those of Sar- from results of other fishes (Clark, 1992; Sen et al. 2001; dinops sagax from North America (Javor 2013), S.sagax Aydin et al. 2004). It can be stated that fishes from dif- ferent regions have different allometric growth of the otolith (Butler et al. 1996), the reason for these

Fig. 4 Relationship between total fish length and otolith length of Fig. 5 Relationship between total fish length and otolith width of S.sindensis from Bandar Lengeh and Qeshm Island (Persian Gulf) S.sindensis from Bandar Lengeh and Qeshm Island (Persian Gulf) Dehghani et al. Marine Biodiversity Records (2016) 9:44 Page 5 of 6

predictors and (or) the predict to obtain linear relation- ships, and even then, this is likely to achieve only approxi- mate linearity. The second, and more serious, drawback is that this method produces asymptotically biased estimates of proportions at age (Francis & Campana, 2004), how- ever, linear regressions between age-otolith size, unlike an- nulus counting methods, to estimate the age structure of the Sardines population need lesser time and cost (Ward et al. 2005; Ward et al. 2012).

Conclusions morphometric relationships are useful tools for testing feeding and for research on fish fossils, especially for determining the size of fish that it is important factor for fish stock monitoring and management. However, for better understanding of otolith growth, it can be recommended for future studies to use the relationships between otolith weight and age, and to measure other oto- lith factors such as area, perimeter, thickness, circularity, and rectangularity.

Abbreviations Fig. 6 Relationship between total fish length and otolith weight of Ancova, analysis of covariance; Anova, analysis of variance; Df, degree of S.sindensis from Bandar Lengeh and Qeshm Island (Persian Gulf) freedom; OL, otolith length; OW, otolith weight; P, probability; R2, coefficient of determination; Sd, standard deviation; TL, total length difference in relationship in different studies, could be Acknowledgements the differences in fish species, habitat, food availability We appreciate and would like to thank the director and staff of the Persian Gulf and Oman Sea Ecological Research Institute for contributions in and physiochemical factors of waters of environment laboratory facilities. that lives there (Aydin et al. 2004; Javor et al. 2011). There are a number of things that could conceivably Funding This work was carried out without any the funding and supporting from produce a shift in the otolith size-body size relationship academic and research centers. in the commercial catch, including large changes in age or sex composition, or changes in regulations, gear, or Availability of data and materials fishing strategies, even different methods used for ana- The data will not be shared with a reason, in this section. lysis (Clark, 1992; Ma et al. 2010). Authors’ contributions The results of this study suggested that otolith dimen- MD carried out biometric and otoliths analysis of fishes, statistical analysis, sions increases as fish length increases and therefore, and writing of paper; EK was superviser and the overall structure of paper otolith growth can be correlated with fish growth. In was confirmed by him; AS assisted in sampling of fishes, and extracting of otoliths; SS cooperated in statistics analysis and writing of paper. All authors addition, the results showed that the otolith length had have read and approved the final manuscript. more correlation to the fish length than otolith weight and -width, respectively, it is similar to study done on Competing interests S.lemuru from Australia (Gaughan and Mitchell, 2000) The authors declare that they have no competing interests. and other fishes (Metin & Ilkyaz 2006; Matic-Skoko Author details et al. 2011). 1Department of Marine Biology, Faculty of Basic Sciences, University of Lombarte and Lleonart (1993) suggested that otolith Hormozgan, P.O.Box: 3995, Bandar Abbas, Iran. 2Department of Stock assessment, Persian Gulf and Oman Sea Ecological Research Institute, development occurs under dual regulation: genetic condi- P.O.Box: 1597, Bandar Abbas, Iran. 3Young Researcher and Elite Clube, Islamic tions regulate the form of the otolith, while environmental Azad University, Bandar abbas Branch, P.O.Bbox: 79159-1311, Bandar Abbas, conditions, mainly temperature in carbonate-saturated Iran. waters, regulate the quantity of material deposited during Received: 16 May 2016 Accepted: 3 June 2016 the formation of the otolith. Butler et al (1996) reported that it was not possible to use otolith weight with other data to estimate age of Pacific sardine. The regression References Aydin R, Calta M, Sen D, Coban MZ. Relationships between fish lengths and method is very appealing in its simplicity but has two otolith length in the population of Chondrostoma regium (Heckel, 1843) drawbacks. It will often be necessary to transform Inhabiting Keban Dam Lake. Pak J Biol Sci. 2004;7:1550–3. Dehghani et al. Marine Biodiversity Records (2016) 9:44 Page 6 of 6

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